JP2000066064A - Optical transmission element, manufacturing method thereof, and optical transmission module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission element and an optical transmission module which can guide received light to a photodetector with efficiency, and has a reduced number of parts and a simple manufacturing process. SOLUTION: In an optical transmission element 80 which is provided with an optical waveguide having a light source 10 and a photodetector 12 enclosed in resin 14, being composed of the other resin 38, 40 together with the former resin, and propagating an optical signal, and which transmits or receives the optical signal, an optical waveguide 40 propagating an optical signal made incident on the photodetector 12 from an optical fiber 24 is structured to be tapered in the cross section toward the photodetector side from the optical fiber side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device, a method for manufacturing the same, and an optical transmission module, and more particularly, to an optical transmission device for performing communication using an optical fiber, a method for manufacturing the same, and an optical transmission module.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Hei 10-126002 discloses an optical transmission system in which a semiconductor laser, a driving circuit, a light receiving element, a current-voltage conversion circuit, and the like are mounted on the same package on a plane and sealed with a lens unit connected to an optical fiber. A module is disclosed.

[0003] In addition, IEICE Journal Vol. 81-
CI, pages 274 to 282 (1998), discloses a semiconductor laser module in which a semiconductor laser is sealed using a resin.

[0004]

In a conventional optical transmission module, a package is sealed with a lens portion. Such an optical transmission module is hermetically sealed by using a glass for the light emitting portion and filling a metal or ceramic package with a nitrogen gas in order to prevent deterioration of the semiconductor laser due to oxidation. Therefore, a package, a glass cap, and the like are required, and joining and sealing of each component are required. Also,
In order to seal nitrogen gas, vacuum baking and hermetic sealing in nitrogen gas are required. As described above, the conventional optical transmission module has a large number of components and a complicated manufacturing process,
There was a problem that the package also became large.

Further, the conventional semiconductor laser module has a structure in which the space between the optical fiber and the semiconductor laser is filled with a resin, and the module is encapsulated with a resin to simplify the assembly process of the module. However, when using this resin encapsulation for the optical transmission module, if the resin optical fiber and the photodetector are to be filled with resin, the core diameter of the plastic optical fiber must be large so that light can be effectively incident on the photodetector. Was difficult. In particular, when performing high-speed optical communication, it is necessary to use a photodetector having a small light receiving area, so that there has been a problem that the amount of received light is reduced and the transmission distance is shortened.

[0006] The object of the present invention, in view of this problem,
An object of the present invention is to provide an optical transmission element and an optical transmission module that efficiently guide light received from an optical fiber to a photodetector, have a small number of components, and have a simple manufacturing process.

[0007]

An optical transmission device having an optical component for transmitting or receiving an optical signal.
The optical component is encapsulated with a resin, and an optical waveguide that transmits the optical signal and is formed of another resin together with the resin is provided.

Further, in the optical transmission device according to the first aspect, the optical component includes a light source and a photodetector, and the optical waveguide propagates an optical signal emitted from the light source to an optical fiber. And an optical waveguide that propagates an optical signal incident on the photodetector from the optical fiber.

Further, in the optical transmission device according to claim 2, a cross-sectional area of an optical waveguide that propagates an optical signal incident from the optical fiber to the photodetector is changed from the optical fiber side to the photodetector side. It is characterized in that it decreases toward.

Further, in the optical transmission device according to any one of claims 2 to 3, the refractive index of the core portion of the optical waveguide is n _core , and the refractive index of the cladding portion is n _clad . When the wavelength of the optical signal is at least one wavelength in the range of 570 nm to 1550 nm, √
(N _core ² −n _clad ² ) ≧ 0.45.

[0011] At least a light source, a photodetector,
An optical transmission element comprising an optical waveguide that propagates an optical signal emitted from the light source to the optical fiber and an optical waveguide that propagates an optical signal incident on the photodetector from the optical fiber, In the optical waveguide, one end of each of the optical waveguides is coupled to the optical fiber, and the photodetector is arranged at the other end of one of the optical waveguides formed by branching on the way, and branched on the way. The light source is arranged at the other end of the other optical waveguide formed.

Further, in the optical transmission element according to claim 5, the light source and the photodetector are sealed with a resin, and the optical waveguide is formed of the resin and a resin forming each optical waveguide. The cross-sectional area of an optical waveguide that propagates an optical signal incident on a photodetector is configured to decrease from the incident side toward the photodetector side, and the one of the ones at a location where each of the optical waveguides branches. The cross-sectional area of the optical waveguide is larger than the cross-sectional area of the other optical waveguide, and the numerical aperture of each of the optical waveguides is larger than the numerical aperture of the optical fiber.

Further, in an optical transmission element including a photodetector and an optical waveguide having an optical waveguide for transmitting an optical signal incident on the photodetector from an optical fiber, the photodetector is sealed with a resin. The optical waveguide is formed of the resin and another resin forming the optical waveguide, and a cross-sectional area of the optical waveguide for transmitting an optical signal incident on the photodetector is defined as the light from the optical fiber side. It is characterized in that it is reduced toward the detector.

Further, in the method for manufacturing an optical transmission element according to any one of claims 5 and 6, one of the tapered slide pins and an insertion hole provided in the one slide pin are provided. The clad portion of each of the optical waveguides is formed by injection molding around a slide pin composed of the other slide pin inserted through, and then the refractive index of the hollow hole from which each slide pin is removed is higher than that of the clad portion. A core portion made of a high core material is formed by injection molding.

Further, in the optical transmission module, one connector portion having an optical transmission element for transmitting or receiving an optical signal and a terminal for inputting or outputting an electric signal to or from the optical transmission element; 8. The optical transmission module according to claim 1, wherein the optical transmission module is configured by joining the two connectors together with the other connector part joined to the optical transmission module. A transmission element, wherein the two connectors are configured to be able to be inserted and removed in the longitudinal direction of the optical fiber.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a plan sectional view showing an optical transmission device according to this embodiment.

In FIG. 1, reference numeral 80 denotes an optical transmission element;
The optical transmission element 80 is a semiconductor laser 1 as a light source for transmission.
0 and a photodetector 12 for reception, and these optical components have a structure sealed with a transparent resin 14.

The semiconductor laser 10 is fixed on a silicon substrate 15 via a metal mount 11, and the signal light emitted from the semiconductor laser 10 is reflected by the rising mirror 16, and then the light source coupling optical waveguide section 38 And the optical fiber 2 further coupled to the light source coupling optical waveguide portion 38
2. Semiconductor laser 10
Is output from the light quantity monitor photodetector 1 formed on the silicon substrate 15 by reflecting light reflected at the end face of the light source coupling optical waveguide section 38.
3 and is used for feedback of the output of the semiconductor laser 10.

The signal light emitted from the optical fiber 24 on the receiving side enters the detector coupling optical waveguide section 40 coupled to the optical fiber 24, and the beam diameter is reduced by the detector coupling optical waveguide section 40. And is incident on the photodetector 12 formed on the silicon substrate 15. The signal converted by the photodetector 12 into a current is
It is configured to be converted into a voltage signal by a preamplifier (not shown) formed above and output.

A separation groove 20 is provided to prevent the light scattered in the optical path from the light emitted from the semiconductor laser 10 from being detected by the photodetector 12. The silicon substrate 15 is fixed to a metal base 19.
The lead frame 17 and the semiconductor laser 10 are connected by bonding wires 21a, and the semiconductor laser 1 is driven by a driving current input to the lead frame 17.
0 is being driven. Similarly, the lead frame 18 and the preamplifier are also connected by a bonding wire 21b, and a signal detected by the photodetector 12 is output from the lead frame 18. A lead frame for supplying power to other grounds (not shown), the light detector 12, the light amount monitoring light detector 13, and the preamplifier is also provided.

As the optical fibers 22 and 24, plastic optical fibers having a core diameter of 980 μm are used. Since these optical fibers have a large core diameter, a detector coupling optical waveguide section 40 having a tapered shape is used to narrow the beam to the photodetector 12 having a small diameter. The optical fibers 22 and 24 are fixed to the male connector 50.

The light source coupling optical waveguide section 38 has an optical waveguide having a substantially constant diameter, and is formed of a transparent resin. The light source coupling optical waveguide section 38 has a smaller diameter than the core diameter of the optical fiber 22 in order to efficiently optically couple to the optical fiber 22. With this configuration, the coupling efficiency does not change even when an alignment error occurs between the optical fiber 22 and the optical transmission element 80. As in the case of the detector coupling optical waveguide section 40, the shape may be such that the diameter increases from the semiconductor laser 10 toward the optical fiber 22, and in this case, the optical fiber 2
The divergence angle of the beam incident on 2 becomes smaller.

On the contrary, the detector coupling optical waveguide section 40 is
The diameter on the optical fiber 24 side is larger than the core diameter of the optical fiber 24, and the diameter on the light detector 12 side is smaller than the diameter of the light detector 12.

In the conventional method of forming the lens structure of the optical transmission element together, if the position shift occurs between the optical fiber and the lens, the focused beam position changes.
A change occurs in the optical coupling efficiency. On the other hand, in the present embodiment, since the lens structure is not adopted, the optical coupling efficiency does not change with respect to the alignment error between the optical fiber and the optical transmission element, and the alignment accuracy between the optical fiber and the optical transmission element is improved. Can be loosened.

Although the optical transmission element 80 does not include a semiconductor laser drive circuit, it can be formed on the silicon substrate 15. In this embodiment, since a plastic optical fiber is used, a wavelength around 650 nm is used for the semiconductor laser 10. Therefore, a PIN photodiode is formed on a silicon substrate 15 for use as a photodetector. As described above, when silicon uses visible light and near-infrared wavelengths having sensitivity, an integrated structure can be adopted as in the present embodiment. When using infrared wavelengths, separately constructed components may be assembled. Further, the silicon substrate 15 also plays a role of radiating heat generated by the semiconductor laser to the metal base 19. Furthermore, the rising mirror 16 may be formed by processing a silicon substrate by etching.

In this embodiment, an edge-emitting semiconductor laser is used, but a surface-emitting semiconductor laser may be used. In that case, the rising mirror 16 becomes unnecessary. The surface-emitting type semiconductor laser also has an effect of generating less heat and improving the reliability of resin sealing.

Further, in the present embodiment, it is not necessary to particularly limit the materials of the core and the clad, and those materials are transparent at the wavelength of the light source to be used and the refractive index of the core material is larger than that of the clad material. It suffices if a predetermined numerical aperture can be obtained by using. For example, acrylic, methacrylic, carbonate, amorphous olefin, sulfone, epoxy, silicone, vinyl, and fluorine compounds can be used in appropriate combination.

As described above, according to the optical transmission device of the present embodiment, the optical components are encapsulated with resin and the optical waveguide structure is formed by the resin itself, so that the number of components is reduced and the size of the optical transmission device is also reduced. can do. In addition, since the optical transmission element is downsized, the optical connector and the optical transmission module can be downsized.

FIG. 2 is a side sectional view of the optical transmission element 80 shown in FIG. 1 as viewed from the photodetector side.

As shown in the figure, the optical transmission element 80 is fixed in the female connector 52. The lead frame 18 is
It is soldered to the substrate 70 of the optical transmission device. The optical fiber 24 is fixed to the male connector 50 after stripping the jacket 26. The male connector 50 is inserted into the female connector 52 of the optical transmission module, and the optical fiber 24
When the positioning of the optical transmission element 80 is performed, transmission and reception of an optical signal become possible.

As described above, since the male connector 50 is mounted so as to be inserted and removed in parallel with the substrate 70, the optical fiber can be easily removed. In the present embodiment, light is input and output perpendicular to the base surface. However, a structure in which light is emitted in parallel to the package without using a rising mirror may be used. In this case, it is desirable to mount the package itself so as to be parallel to the substrate.

Next, FIG. 3 shows the relationship between the shape and size of the optical waveguide section 40 for coupling to a detector shown in FIGS. 1 and 2 and the optical constants.
This will be described with reference to FIG.

The optical waveguide unit 40 for coupling a detector according to the present embodiment.
As shown in the figure, a light guide is constituted by a tapered optical waveguide, and by narrowing the light, it is possible to efficiently guide the light to a photodetector having a small area even when using a large core-type optical fiber. . Here, for the sake of simplicity, it is assumed that the diameter of the optical fiber joint portion 44 of the detector coupling optical waveguide portion 40 is the same as the core diameter of the optical fiber 24. The light propagating through the optical fiber 24 is transmitted through the core 3 of the optical fiber 24.
Since the light propagates while causing total reflection at the interface between the cladding 4 and the cladding 36, only light rays that form a certain angle with respect to the optical fiber 24 can pass through the optical fiber 24. Here, assuming that the refractive index of the core 34 of the optical fiber 24 is n _cf and the numerical aperture is NA _f , when the maximum allowable angle of the light beam that can be transmitted through the optical fiber 24 with respect to the optical fiber 24 is ψ, ψ = sin ⁻¹ (NA _f / n _cf ) (1)

Here, in general, the numerical aperture NA of the optical fiber and the optical transmission element is as follows: when the refractive index of the _core is n _core and the refractive index of the cladding is n _clad , NA = √ (n _core ² −n _clad ² ) (2)

The conditions under which the light propagating at the maximum angle に 対 す る with respect to the optical fiber 24 is totally reflected and propagated in the tapered detector coupling optical waveguide section 40 until reaching the photodetector 12 will be described. . Assuming that the angle of the tapered portion of the detector coupling optical waveguide section 40 is α, the incident angle of this light beam on the optical waveguide interface is expressed as π− (ψ + α). Therefore, when the numerical apertures of the optical fiber 24 and the detector coupling optical waveguide section 40 are equal, this light ray does not cause total reflection, and most of the light passes through the optical waveguide interface. The present invention is characterized in that the numerical aperture of the detector coupling optical waveguide section 40 is made larger than the numerical aperture of the optical fiber 24.

Here, the angle of incidence on the optical waveguide interface at the time of the n-th reflection at the interface of the detector coupling optical waveguide section 40 is expressed as π − {+ (2n−1) α}. The condition for causing this light to undergo total reflection at the interface of the optical waveguide is as follows: When the refractive index of the core 30 of the optical waveguide unit 40 for detector coupling is n _cw and the numerical aperture is NA _w , (NA _w / n _cw ) ≧ sin ｛ψ + (2n−) α｝ (3)

In order for the light propagating at an angle に 対 し て with respect to the optical fiber 24 to be reflected no more than n times,
The length 1 of the detector coupling optical waveguide section 40 is

[0039]

(Equation 1)

It is necessary to satisfy the following.

Here, the radius of the optical fiber joint 44 is R
When the radius of the core 30 at the i-th number of reflections is d _i , assuming that ξ _i = ψ + 2iα (5), d _i = 2y _i / (tan α + tanξ _i ) (6) Here, y ₁ = R (7). y _i is obtained using the recurrence formula y _i = (− tan α + tan ξ _i−1 ) / (tan α + tan -1 _i−1 ) (8).

Accordingly, the radius r of the detector junction end 48 is calculated from r = R-ltan (α) (9) To make this r as small as possible,
It is desirable to set α and l. By selecting the shape and optical constants of the detector coupling optical waveguide section 40 so as to satisfy the equations (3) and (4), ideally, the light enters the detector coupling optical waveguide section 40 from the optical fiber 24. All light rays can be totally reflected at the interface of the detector coupling optical waveguide section 40 and can reach the photodetector 12, so that the light use efficiency can be increased. The effect of improving the photodetection sensitivity by reducing the beam diameter using this tapered shape is greater when the core diameter is larger, and is usually used when bonding with a plastic optical fiber having a core diameter of 0.5 mm or more, particularly a commonly used core diameter of about 1 mm. The effect is great when used for.

FIG. 4 shows the taper angle α of the detector-coupling optical waveguide section 40 and the reduction ratio r / R of the diameter of the tapered optical waveguide calculated using the equations (1) to (9).

As shown in the figure, in order to obtain the same reduction ratio r / R, it can be seen that the larger the number of reflections n, the smaller the taper angle α. In general, the smaller the taper angle α is, the easier it is to manufacture the optical waveguide unit 40 for detector coupling.

[0045] Figure 5 shows the reduction ratio r / R of the diameter of the formula (1) the numerical aperture NA _W of the optical transmission element were calculated using equation (9) and a detector coupled optical waveguide section 40.

In the calculation, NA _f = 0.3, NA _w
= 0.5, n _cf = n _cw = 1.5, the equation (3) is equal, and the value that maximizes l is used in the equation (4).

As shown, the refractive index NA _w of the optical waveguide is shown.
It can be seen that the larger the beam, the greater the effect of beam reduction. It should be noted that n = 2 and 3 show almost the same characteristics.

From the above results, the desirable number of reflections n is 1
３3, and it can be said that n = 2 is particularly desirable.

Here, NA _f = 0.3, NA _w = 0.
When 5, _ncf = 1.5, R = 0.5 mm, and n = 2, 1 = 4.9 mm and r = 0.29 mm, and the beam diameter can be reduced to 58%. The energy density of light can be increased three times. As is apparent from FIG. 5, when the numerical aperture of the optical transmission element 80 is set to be 1.5 times or more the numerical aperture of the optical fiber 24 to be joined,
If the area ratio can be 0.4 or less, and if the numerical aperture of the optical fiber 24 is twice or more, the reduction ratio of the beam diameter can be 0.5 or less, and the area ratio can be 0.25 or less. it can. Usually, in a plastic optical fiber, a numerical aperture of 0.3 is used for high-speed communication. Therefore, a numerical aperture of the optical waveguide unit 40 for detector coupling is 0.45.
As mentioned above, if possible, it is desirable to be 0.6 or more. Also,
Usually, the wavelength used for optical communication is from 570 nm to 1
It is about 550 nm, and it suffices that the numerical aperture is not less than the numerical aperture at a wavelength used within this range.

As described above, the optical waveguide portion 4 for coupling the detector is used.
A numerical aperture of 0, that is, a larger refractive index difference between the core portion 30 and the clad portion 32 is preferable because the effect of light confinement is increased. In order to increase the numerical aperture, a dielectric film having a low refractive index may be formed at the interface between the core 30 and the clad 32. Further, when a metal film is further formed at the interface between the dielectric film and the clad portion, the beam diameter exceeds the numerical aperture, and the beam transmitted through the dielectric film is reflected back by the metal film, so that the beam diameter can be further reduced.

FIG. 6 is a perspective view of an optical transmission module using the optical transmission element according to the present embodiment.

In the figure, an optical transmission element (not shown) is fixed in the female connector 52. The optical transmission module 82 is soldered and fixed to a substrate of an optical transmission device (not shown) using the lead frame 18. The optical transmission module 82 inserts the male connector 50 into the female connector 52 and transmits and receives an optical signal. Here, the male connector 50 and the female connector 52 are locked 5
4 fixed. In the present embodiment, since the alignment accuracy between the optical fibers 22 and 24 and the optical transmission element 80 may be low, the male connector 50 and the female connector 52 may be used.
The whole can be made by injection molding integrally using plastic. The joint between the male connector 50 and the female connector 52 does not need to be suppressed to a severe dimensional error, and may be a plastic material.

Next, a method for manufacturing the optical transmission element 80 will be described with reference to FIG.

First, a semiconductor laser 10 and a rising mirror are fixed via a mount on a silicon substrate 15 on which a photodetector 12, a preamplifier, and a photodetector 13 for monitoring light quantity are formed in advance. Fixed to. Next, a semiconductor laser 10, a photodetector 12,
The preamplifier, the light amount monitoring photodetector 13 and the lead frame 17 are bonded with bonding wires. Although not shown, the base 19 and the lead frame 1
7 is connected to facilitate molding. Next, as shown in FIG. 7A, each component of the optical transmission element 80 is placed in a mold 60, and a resin forming a clad portion is injected from an injection port 62. The injection of the resin also encapsulates the optical element. After the resin has hardened, the mold 62 is opened in the vertical direction in the figure, and the molded part is taken out. Subsequently, FIG.
As shown in (b), the molded component is placed in a mold for molding the waveguides 38 and 40, and the injection port 63a and the injection port 6 are placed.
3b, a resin serving as a core material is injected into the detector coupling optical waveguide portion 40 and the light source coupling optical waveguide portion 38 to form the core portion. After the resin has hardened, the mold 62 is opened in the vertical direction in the figure, and the optical transmission element 80 shown in FIG. 7C is taken out. After removal, as shown in FIG. 7 (c), the core has a structure in which resin is also applied to the resin-injected portion, and this portion is polished to form a light emitting portion and a light incident portion. Finally, disconnect the connection between the base and the lead frame.

According to the manufacturing method of the present embodiment, since the optical component can be sealed by injection molding, the number of manufacturing steps is reduced and simplified. In the above manufacturing method, the clad portion and the core portion are formed in this order, but the core portion may be formed in advance, and then the clad portion may be formed. In this case, it is desirable that the mold be opened in a direction perpendicular to the plane of FIG. Further, the optical component may be covered with a core material. Further, in addition to the injection molding method described above, a method such as an ultraviolet curing method, a wet etching method, a reactive ion etching method, and a photopolymerization method may be appropriately selected to form an optical transmission element or an optical waveguide.

Next, an optical transmission device according to a second embodiment of the present invention will be described with reference to FIGS.

FIG. 8 is a plan sectional view showing a part of the optical transmission device according to the present embodiment.

The optical transmission element 80 of the present embodiment is assumed to perform bidirectional optical communication using one fiber 22, and as shown in FIG. The waveguide section 38 and the optical waveguide section 40 for detector coupling are embedded.

The light source junction 4 of the light source coupling optical waveguide section 38
The semiconductor laser 10 is provided in 6, and the photodetector 12 is provided in the detector junction 48 of the optical waveguide unit 40 for detector coupling. The detector coupling optical waveguide section 40 has a shape obtained by cutting out a part of a cone, and is configured such that the diameter increases from the detector junction section 48 side to the optical fiber coupling section 44. The light source coupling optical waveguide 38 has a cylindrical shape and a substantially constant thickness. Both are connected to the optical fiber 22 at the optical fiber joint 44.

The optical signal from the semiconductor laser 10 is output to the optical fiber 22 through the light source coupling optical waveguide 38, and the optical signal sent through the optical fiber 22 passes through the detector coupling optical waveguide 40. Light detector 12
Is detected by

As described above, according to the present embodiment, bidirectional communication is performed by using one optical fiber 22, so that the optical fiber is compared with a case where one optical fiber is used for each of transmission and reception. The number of fibers can be reduced, and an optical fiber can be laid at low cost. Further, the connection between the optical fiber and the optical transmission device becomes easy.

Next, the relationship between the shape and dimensions of the light source coupling optical waveguide 38 according to the present embodiment and the optical constants will be described. In addition, about the optical waveguide part 40 for detector coupling,
The description is omitted because it is the same as that of the first embodiment.

The conditions under which a light beam incident on the optical fiber 22 from the light source coupling optical waveguide section 38 is totally reflected at the interface of the optical fiber 22 will be described.

When the divergence angle of the light beam from the light source is 光線, the aperture NA _s of the light source is expressed as NA _s = sinΘ (10), the refractive index of the optical fiber 22 is n _cf , and the divergence angle Θ
If the divergence angle of the light beam when the light beam enters the optical fiber 22 is represented by θ, then θ = sin ₋₁ (NA _s / n _cf ) (11)

Further, assuming that the inclination of the light source coupling optical waveguide section 38 is β, in order for this light ray to be totally reflected at the interface of the optical fiber 22, NA _s / _ncf ≧ sin (θ + β) (12) There is a need.

Here, by increasing β, the distance between the semiconductor laser 10 and the photodetector 12 can be widened, so that the mounting of the semiconductor laser 10 and the photodetector 12 becomes easy. At this time, it is necessary to reduce θ, and it is desirable that the divergence angle の of the light beam that enters the light source coupling optical waveguide portion 38 among the light beams from the semiconductor laser 10 is small. Therefore, one example of the semiconductor laser 10 suitable as a light source used in the optical transmission device of the present invention is a surface-emitting type semiconductor laser.
Usually, the spread angle of a surface emitting semiconductor laser is 1 / e ² An about 5 ° in one-byte, the NA _s is about 0.09. Therefore, NA _f = 0.3, NA _s = 0.1, n _cf =
Assuming that 1.5, β should be 7.7 ° or less, and if the radius of the light source coupling optical waveguide section 38 is s, NA _w =
0.5, n _cw = 1.5, R = 0.5 mm, r = 0.29
When mm, s = 0.125 mm, l = 4.3 mm, and n = 2, the distance between the light source joint 46 and the detector joint 48 is 0.5 mm. Numerical aperture NA _f = 0.3 for high-speed communication
Equation (10) for the plastic optical fiber 22 of
If the in represented by NA _s and 0.1 or less, it is possible to widen the distance between the light source coupling optical waveguide 38 and the detector coupling optical waveguide portion 40. When the divergence angle of the light source is large, such as when an edge emitting type semiconductor laser or a light emitting diode is used as the light source, the light source and the light source coupling optical waveguide 3 are used.
Between 8, a pinhole for limiting the spread angle may be provided. In such a case, the light source coupling optical waveguide 38 may be tapered so that the cross-sectional area increases from the light source junction 46 to the optical fiber junction 44.
When the light beam from the light source has an intensity distribution, the 1 / e ² half angle of the intensity distribution may be used as the spread angle の in Expression (10).

Further, by integrating the light source and the photodetector, the distance between the light source joint 46 and the detector joint 48 can be reduced.

Further, by making the diameter of the light source coupling optical waveguide 38 smaller than the diameter of the optical fiber joint 44,
It is possible to increase the ratio of the amount of light that is branched to the detector coupling optical waveguide portion 40 among the amount of light incident from the optical fiber 22. Since the branching ratio is almost proportional to the area of each optical waveguide section, for example, if the diameter of the light source coupling optical waveguide section 38 is set to １ ／ of the diameter of the optical fiber joint section 44, the light source coupling optical waveguide section 38 and the detection path are detected. The ratio of the ratio of the amount of light branched to the optical waveguide for coupler coupling 40 is approximately 1: 9. The diameter of the light source coupling optical waveguide section 38 is set to 1 / the diameter of the optical fiber joint section 44.
By setting it to 4 or less, the light loss can be made 10% or less. Further, when the diameter of the light source coupling optical waveguide section 38 is set to be 1/10 or less of the diameter of the optical fiber joint section 44, the optical loss becomes 1
% Or less. Therefore, the core radius is 0.5 m
When the plastic optical fiber 22 of m is used, the radius of the optical waveguide portion 38 for coupling the light source should be 0.125 mm or less, preferably 0.05 mm or less, with respect to the radius of the optical fiber joint portion 44 of 0.5 mm. desirable.

Next, a method of manufacturing the optical transmission device according to the present embodiment will be described with reference to FIG.

First, as shown in the figure, the mold 60 has a tapered slide pin 64 and a linear slide pin 66 attached thereto.
Insert. The linear slide pin 66 is inserted into the mold 60 through a hole 68 formed in the tapered slide pin 64. Next, the clad material is melted and injected into the mold 60 through the injection port 62. After the mold 60 is cooled and the clad material is solidified, the tapered slide pin 64 and the linear slide pin 66 are pulled out. Thereafter, the clad portion is placed in a core material injection mold (not shown), and the core material is injected into the hollow hole after the pulled-out slide pin to form a core portion. Finally, the portion corresponding to the injection port of the core material is subjected to polishing or heat treatment for planarization.

As described above, according to the manufacturing method of the present embodiment, it is possible to easily manufacture an optical waveguide having an integrated structure of the light source coupling optical waveguide and the detector coupling optical waveguide.

In this embodiment, polystyrene (refractive index: 1.59) is used as the core material, and polymethylpentene (refractive index: 1.46) is used as the cladding material. At this time, the numerical aperture is 0.63 at a wavelength of 650 nm, and if the number of reflections is n = 2 from FIG. 5, the reduction ratio can be 0.4 and the area ratio can be 0.16.

[0073]

As described above, the optical transmission device of the present invention has the following features.
Since the light source and the photodetector were sealed with resin and the optical waveguide of the optical signal was formed with another resin together with the resin,
Even if an optical fiber having a large core diameter is used, the light received from the optical fiber can be efficiently guided to the photodetector, and the number of parts can be reduced. Further, according to the method for manufacturing an optical transmission element of the present invention, an optical transmission element can be manufactured by a simple manufacturing process. Furthermore, a compact optical transmission module can be provided by configuring an optical transmission module using the optical transmission element of the present invention.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing an optical transmission device according to a first embodiment of the present invention.

FIG. 2 is a side sectional view of the optical transmission element 80 shown in FIG. 1 as viewed from a photodetector side.

FIG. 3 is a view for explaining the relationship between the shape and dimensions of the optical waveguide unit 40 for detector coupling shown in FIGS. 1 and 2 and the optical constants.

FIG. 4 shows the taper angle α of the detector-coupled optical waveguide section 40 shown in FIGS. 1 and 2 and the reduction ratio r / of the diameter of the tapered optical waveguide.
It is a figure showing the relation with R.

FIG. 5 shows a numerical aperture NA _W of the optical transmission element 80 shown in FIGS. 1 and 2 and a reduction ratio r / of the diameter of the optical waveguide unit 40 for detector coupling.
It is a figure showing the relation with R.

FIG. 6 is a perspective view of an optical transmission module using the optical transmission element according to the first embodiment.

FIG. 7 is a diagram illustrating a method of manufacturing the optical transmission device according to the first embodiment.

FIG. 8 is a plan sectional view showing a part of an optical transmission device according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram of a method for manufacturing an optical transmission device according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 10 semiconductor laser 11 mount 12 photodetector 13 photodetector for light quantity monitoring 14 transparent resin 15 silicon substrate 16 rising mirror 1718 lead frame 19 base 20 separation groove 21a, 21b bonding wire 2224 optical fiber 26 jacket 30 optical waveguide core 32 optical guide Waveguide cladding 34 Optical fiber core 36 Optical fiber cladding 38 Optical waveguide for light source coupling 40 Optical waveguide for detector coupling 44 Optical fiber junction 46 Light source junction 48 Detector junction 50 Male connector 52 Female connector 54 Lock 6061 Mold 6263, a63b Injection port 64 Tapered pin 66 Linear pin 68 Coupling hole 70 Substrate 80 Optical transmission element 82 Optical transmission module

Claims (9)

[Claims] 1. An optical transmission element having an optical component for transmitting or receiving an optical signal, wherein the optical component is encapsulated with a resin, and an optical waveguide for transmitting the optical signal formed of another resin together with the resin. An optical transmission element comprising a wave body. 2. The optical device according to claim 1, wherein the optical component includes a light source and a photodetector, and the optical waveguide includes an optical waveguide for transmitting an optical signal emitted from the light source to an optical fiber, and the optical waveguide. An optical waveguide for transmitting an optical signal incident on the photodetector from a fiber. 3. The optical waveguide according to claim 2, wherein a cross-sectional area of an optical waveguide for transmitting an optical signal incident on the photodetector from the optical fiber decreases from the optical fiber side toward the photodetector side. An optical transmission element, characterized in that: 4. The method according to claim 2, wherein
In one embodiment, when the refractive index of the core portion of the optical waveguide is n _core and the refractive index of the cladding portion is n _clad , the wavelength of the optical signal is 570.
An optical transmission element characterized in that √ (n _core ² −n _clad ² ) ≧ 0.45 in at least one wavelength in a range from nm to 1550 nm. 5. At least a light source, a photodetector, an optical waveguide for transmitting an optical signal emitted from the light source to an optical fiber, and an optical waveguide for transmitting an optical signal incident on the photodetector from the optical fiber. An optical waveguide comprising: an optical waveguide composed of a waveguide and one end of each of the optical waveguides, one end of each of the optical waveguides being coupled to the optical fiber and branching in the middle of the other optical waveguide. An optical transmission element, wherein the photodetector is arranged at one end, and the light source is arranged at the other end of the other optical waveguide that is formed by branching on the way. 6. The optical detector according to claim 5, wherein the light source and the photodetector are sealed with a resin, and the optical waveguide is made of the resin and a resin forming each of the optical waveguides. The cross-sectional area of the optical waveguide that propagates the optical signal is configured to decrease from the optical fiber side toward the photodetector side,
The cross-sectional area of the one optical waveguide at a location where each of the optical waveguides is branched is larger than the cross-sectional area of the other optical waveguide, and the numerical aperture of each of the optical waveguides is larger than the numerical aperture of the optical fiber. An optical transmission element, characterized in that: 7. An optical transmission device comprising: a photodetector; and an optical waveguide having an optical waveguide for transmitting an optical signal incident on the photodetector from an optical fiber, wherein the photodetector is sealed with a resin. The optical waveguide is formed of the resin and another resin forming the optical waveguide, and a cross-sectional area of the optical waveguide for transmitting an optical signal incident on the photodetector is defined as the light from the optical fiber side. An optical transmission element characterized in that it is made smaller toward the detector. 8. The method according to claim 5, wherein
In the method for manufacturing an optical transmission element according to one of the claims, around a slide pin composed of one slide pin having a tapered shape and the other slide pin inserted through an insertion hole provided in the one slide pin, The clad portion of each of the optical waveguides is formed by injection molding, and then, in the hollow hole from which the slide pins are removed, a core portion made of a core material having a higher refractive index than the clad portion is formed by injection molding. A method for manufacturing an optical transmission element. 9. An optical transmission element for transmitting or receiving an optical signal, one connector portion having a terminal for inputting or outputting an electric signal to or from the optical transmission element, and the other connected to an optical fiber. An optical transmission module comprising: a connector section; and the two connectors are coupled to each other, wherein the optical transmission element is the optical transmission element according to any one of claims 1 to 7, The optical transmission module according to claim 1, wherein the two connectors are configured to be detachable in a longitudinal direction of the optical fiber.